The invention relates to a method for compensating structural vibrations of an aircraft caused by external influences, especially wind gusts, turbulence, and buffeting, in particular compensating structural vibrations of a manned fixed-wing aircraft, a missile, or a helicopter, as well as a system for performing this method.
Another viewpoint of the invention is the so-called buffeting or xe2x80x9cshaking,xe2x80x9d in other words the response of the behavior of the aircraft as a result of separated air flow (xe2x80x9cbuffetxe2x80x9d) and vortices at high angles of attack. The dynamic loads from the process of separated flow are high and result in design criteria for the wings and empennage of aircraft, especially manned fighter aircraft. Weakening of the effects of these disturbances is therefore very important in designing aircraft and in increasing and monitoring the load limits of aircraft.
The behavior of an aircraft in flight in a turbulent atmosphere should be as calm as possible, but should lie at least in the range of known rules. This is especially true of passenger aircraft for which there are special requirements regarding passenger comfort, also called xe2x80x9cride comfort.xe2x80x9d External disturbances, especially wind blasts and turbulence, act directly on structural parts of the aircraft which are excited to vibrate as a result of the shapes of the structures. Because of this effect, the behavior during flight, and especially the comfort of the passengers and pilots, are unfavorably influenced and the structure of the aircraft is subjected to loads.
Thus far, to reduce the effects of such external atmospheric disturbances on the aircraft, sensor devices, especially acceleration sensors, have been mounted at various locations on the aircraft. Preferably, acceleration sensors were placed at the tips of the wings, on the fuselage, and at the tips of the vertical and horizontal stabilizers. The sensor signals are processed in a controller and considered in determining the adjustments of the drives of the rudder surfaces. Such systems are described for example in xe2x80x9cProceedings of the 26th Aircraft Symposium,xe2x80x9d Sendai, Japan, October 19-21, xe2x80x9cJapan Publications Trading Company,xe2x80x9d Tokyo, 1988, pages 160-163 or in xe2x80x9cDGLR Paperxe2x80x9d 084-094 of the Deutsche Gesellschaft fxc3xcr Luft- und Raumfahrt, Annual Meeting, Oct. 1-3, 1984, Hamburg.
One disadvantage of these sensor devices or systems is that the cost of measurement technology and the expense for regulating and adjusting devices is very high. Especially in controlled aircraft, the cost is further increased by the fact that in the event of an error in such sensor devices, appropriate error recognition and system reconfiguration functions must be provided to at least limit the effects of such errors or to compensate for them.
In addition, methods and systems for compensating disturbances in aircraft structures are known from U.S. Pat. Nos. 4,905,934, 5,072,893, 5,186,416, and 4,725,020. These patents are intended to reduce the loads on the structure caused by these disturbances. Acceleration signals or these signals combined with stress values and attack angles are used to move the control surfaces of the aircraft so that the load distribution in the structure is reduced. Higher frequency forms of vibration and structural couplings are not compensated however. Phase delays, which play an important role particularly at higher frequency vibrations, are not taken into account so that the method according to the prior art is suitable only for very low frequencies.
Hence, the goal of the present invention is to provide a method and device for compensating structural vibrations of an aircraft caused by wind gusts and buffeting that is also suitable for compensating higher frequency vibrations.
This goal is achieved by a method for compensating structural vibrations of an aircraft caused by wind blasts and buffeting on the aircraft in flight, the method including the steps of: (1) detecting structural vibrations by measurement technology using roll rates determined in an inertial sensing system; (2) feeding the disturbing parameters detected to a flight control system; and (3) producing phase- and amplitude-correct control flap movements by generating appropriate control signals at the respective drives to counteract the phases and amplitudes of the excited vibrations. A device for performing the method is also provided. Additional embodiments are described herein.
In the method according to the invention or the device according to the invention, the cost of the equipment is extremely low and, depending on the flight control system in question, comprises additional connections between the inertial sensing system of the flight control system and the actual flight control systems. In addition, there is a functional cost for in-phase processing of the values fed back from the inertial sensing system for damping the behavior in flight. This expense is much greater in the method according to the prior art because devices must be provided to supply the signals of the acceleration sensors in-phase and to monitor them. If it is assumed that an inertial sensing system and a flight control system are already aboard the aircraft in question, a flight control system is only functional in feeding back additional values from the inertial sensing system for damping the behavior of the aircraft in flight.
Surprisingly, it has been found that the effects of atmospheric disturbances on an aircraft in flight can essentially be detected with only the roll rates from an inertial sensing system designed for a flight control system and that these effects can be damped by appropriately supplying and processing these values in the flight control system.